The barn owl auditory system provides an excellent model for studying the mechanisms by which experience during development shapes the function and organization of the adult brain. In the barn owl, early visual experience calibrates the processing of auditory spatial information in two midbrain nuclei specialized for sound localization. A pathway through the forebrain that processes auditory spatial information in parallel with these nuclei has recently been described. Results from preliminary experiments indicate that the representation of auditory space in the forebrain is also influenced by early visual experience and suggest that the forebrain may be essential for guiding experience-dependent changes in the representation of auditory space in the midbrain. The goals of this research are 1) to characterize visually-guided changes in the representation of auditory space in the forebrain sound localization pathway; 2) to identify the site of visually guided plasticity in the forebrain; 3) to determine the role of the forebrain in guiding experience-dependent changes in the midbrain pathway; and 4) to characterize neurophysiological interactions that might exist between the forebrain and midbrain pathways. This research will reveal general principles of brain development, consequences of abnormal experience early in life and strategies used by the brain to deal adaptively with sensory challenges. These experiments will also provide insight into the brain's ability to use alternate pathways to minimize functional deficits caused by localized damage. The results could aid the development of treatment strategies for a wide variety of human dysfunctions, particularly those resulting from birth defects, childhood disease, or injuries which cause or are associated with abnormal environmental influences on brain development.